To do a Diff is to power level a character on an MMORPG from the bottom to the top level available in record amount of playing time. MOST who do this, have intentions of their account going to a Ni Hao website (Ni Hao = gold farmer)

(Lumathus):Man where did all our tanks go? they all went to healing spec! argh!
(Unregistered): hmm maybe I should do a diff with my druid so we have a tank in guild eh.

As Digitus and the Asian girl are IMing...
Digitus asked, "Hey, u wanna go to the movies?"
The Asian girl replied, "No, let's do something diff. Let's go into a forest."
Digitus asked, "Why? Do you wanna do it? Cuz I do."
The Asian girl replied, "Yeah, let's go to the one over by the ice cream place and bring a condom, ok?"
Digitus replied, "Yeah, I got it. See ya."
The Asian girl said good-bye as they logged off.